Electron discharge rectifier



W.T. MlLLls ELECTRON DISCHARGE RECTIFIER Filed sept. 14, 1959 H 7 l 7 37 3 5 3 3 Il 9 3 l. H 5 2 f im 4 I 3 b 1| u f 9 l llll .i 3 l l--uunnmwHHMll 3 9 9 )l :lll 9 4 Il 2 .1P Lll 4 7 RRHH H @I ---lllTIII -l Jun, f|| ---l nnfwwHnwl l 1 5 9 3 9 l 5 M .1 I 3 3 l 3 5 2 .n 7 4 5 Aug.7, 1962 FIG.3

FIG.

FIG. 2

ite States 4arent @dice 3,048,726 ELECTRON DISCHARGE RECTIFIER Walter T.Mllis, Owensboro, Ky., assignor to General Electric Company, acorporation of New York Filed Sept. 14, 1959, Ser. No. 839,794 11Claims. (Cl. 313-3) My invention relates t-o electron discharge devices,and more particularly to an improved electron discharge device of therectifier type.

Rectifier tubes for receiver operation have heretofore been constructedwith either directly or indirectly heated cathodes, depending on themagnitude of the voltages to be rectified thereby, as well as on otherenvironmental factors.

Such tubes, when constructed in accordance with techniques heretoforedescribed, are subject to destructive arc-over, especially during acritical warm-up period when the anode potential and the heater voltageare applied simultaneously.

Quick-warm-up cathodes are extremely `desirable for rectifier tubeoperation because (1) the probability of arc-over between cathode andanode is materially reduced according as the Warm-up period for thecathode is reduced, (2) for shorter warm-up periods, the rectifier loadimpedance is more `apt to be maximized in yany given circuitarrangement, especially if the rectifier reaches normal operatingtemperature before the other tubes in the circuit. The maximum loadimpedance operates to limit the current drawn during arc-over, thusminimizing injury to the rectifier cathode coating.

Directly heated cathodes in the form of filamentary members capable,when heated, of emitting copious supplies of electrons, have been usedto advantage for relatively low-voltage operation because such cathodesare characterized by shorter warm-up periods, which, in turn, resultfrom the lower thermal capacity of such cathodes. However,directly-heated cathode rectifiers cannot `satisfactorily be used forrelatively high-voltage application because of the inherent mechanicallimitations of such cathodes.

yFor relatively high-voltage applications, such as damper rectifierscommonly employed lin television, indirectly heated cathodes have beenused yfor mechanical strength. In such rectifiers, the warm-up yperiodis commonly long as compared to that of other tubes in such circuits.Accordingly, in such tubes, the arc-over problem is appreciable and thisproblem is further aggravated by the fact that the peak voltages to .berectified are very high, which, in turn, has led to the introduction ofa substantial amount of high temperature insulation in theheater-cathode construction. The high-temperature insulation possesseshigh thermal capacity, which causes a lengthening of the warmup time.This, as noted above, operates to increase the probability of arc-over.Accordingly, -in the construction of such damper rectifiers, one hasheretofore been confronted with a compromise selection of utilizing, onthe one hand, a minimal amount of heater-to-cathode insulation toachieve short warm-up time, and sufficient insulation, on the otherhand, to prevent high-voltage breakdown. This compromise was, at best,an unsatisfactory condition resulting as it did in manufacture ofrectifiers of limited utility.

lt is, therefore, a primary obje-ct of this invention to provide animproved rectifier of the electron discharge type which is free from theabove-noted difficulties.

Another object of this invention is to provide novel and improvedcathode arrangements for rectifier tubes whereby a short warm-up timefor such rectifiers is readily accomplished.

Still another object of this invention is to provide an improvedelect-ron discharge rectifier device having novel cathode arrangementswhereby such rectifier device is capable of low cathode Warm-up timeunder a wide variety of `operating characteristics.

`In the accomplishment of the foregoing objectives, I provide, inaccordance with one aspect of my invention, a new rectifier arrangementin which the cathode is generally of the directly heated type, therebyto realize the advantage residing in the inherently low-thermal capacitythereof. However, in lieu of the coated-wire or ribbon types ofdirectly-heated cathode, which, as discussed above, suffer inherentmechanical weakness, I provide relatively rigid, cylindrical sleevemembers of novel construction through Which the heating current isdirectly conducted, thereby to achieved the requisite mechanicalstrength to overcome any tendency toward bowing, vibration, or otherdeformation of the cathode under the influence of high-intensitycathode-anode fields.

In accordance with another aspect of my invention, I provide a rectierdevice in which the cathode is in the form of a pair of tubularconductive members disposed in parallel spaced relation, each bearing anexternal coating of electron-emissive material, the members beinginterconnected at one end, the other ends of the members providing inputand output terminals for applying heating current through the members,in series.

lFor a better understanding of my invention, reference may be had to thefollowing description taken in connection with the accompanying drawing,and its `scope will be pointed out in the appended claims.

FIG. 1 is a perspective view, with parts broken away, of an electrondischarge tube constructed in accordance with one form of my invention.

`iFIG. 2 is a fragmentary elevational view showing a modified form ofcathode construction which can be ernployed in the tube of FIG. 1.

iFlG. 3 is a fragmentary elevational View of another modified form ofcathode construction according to my invention.

Referring now to the drawing, I have shown, in FIG. 1, an electrondischarge device in the form of a double-diode rectifier tube 11constructed in accordance with my invenltion. It will be understood thatthe features of this invention may be utilized with equal effectivenessin ysingle diode yarrangements as Well as in assemblies having anydesired number of functional tube elements.

As shown, the rectifier 11 comprises a pair of diode subassemblies 13and 15 which are of su-bstantially identical construction. Accordingly,in the following description, the elements of subassembly 13 will bedescribed in detail, the corresponding elements of subassembly 15 being`assigned similar reference numerals with associated superscripts orprime characters. Thus, the subassemblies include -anodes or plates 17,17' and cathodes 19, 19', mounted -in coaxial yspaced relationtherefrom, the anodes and cathodes being supported within an evacuatedenvelope 21 between upper and lower insulative spacers or micas 23, 25.

The anodes 17, 17 can be of any suitable material for the purpose. In asuccessful operative embodiment, I have employed to advantage `aplural-layer material consisting of a layer of copper over which is alayer of aluminum-clad iron, as described and claimed in my copendingapplication, S.N. 764,988, filed October 2, 1958, entitled ElectronDischarge Device, and assigned to the assignee of this application.

The anode 17 is formed to provide two parallel tubular portions 27, 29,which may be conductively joined together along their adjacent sidewalls by an axially extending web portion 31, which, in turn, may beprovided with a transversely projecting fin portion 33 of axialdimension substantially equal to those of the tubular portions 27, 29.Such fin portion 33 has been found to be desirable for dissipatingrelatively large quantities of heat that are generated in the anoderegions between the tubular port-ions 27, 29". Projecting from the outerside walls of the tubular portions 27, 29 and in diametrally opposed,coplanar relation to the web portion 31, are additional n portions 35,37 as required, which carry tabs 39 at top and bottom which may, inturn, pass through suitable openings in top and bottom micas 23, 25 forsecuring the anode therebetween and for providing a terminal to which ananode stem lead 41 may be secured as by spot welding.

The cathode 19 is formed to provide two parallel tubular portions 43,45, which are coaxially disposed within the anode portions 27, 29,respectively, and in relatively closely spaced relation thereto. It willbe appreciated that extremely small cathode-to-anode spacing can thus berealized inasmuch as the tubular construction of the cathode portions43, 45 resists bowing, vibration, or other mechanical deformation.

The cathode portions 43, 45 are preferably of a highresistivity, highhot-strength material of the type disclosed and claimed in my U.S.Patent No. 2,878,410, patented March 17, 1959, entitled Electronic TubeStructure and assigned to the assignee of the present application. In asuccessful operative embodiment, a cathode material consisting ofnickel-clad Inconel was used, the lnconel component being a low-thermaleX- pansion, low-thermal conductivity alloy available through theInternational Nickel Company, and, according to standard handbooks ofmetallurgy, has the following percentage composition by weight:

The tubular cathode portions 43, 45 may be formed in any suitableconventional manner to provide a smooth cylindrical surface with a lockseam, lap seam, or simple butt seam, as desired, the outer surface ofthe portions 43, 45 being coated, in any suitable manner, with anelectron emissive material which, upon heating, provides a copioussupply of electrons. The upper ends of the cathodes are passed throughsuitable openings in the top mica and are provided with conductive tabs47, 49, which are bent toward each other and spot welded together toprovide electrical continuity between the portions 43, 45. The lower endof cathode portion 45 carries a tab 51 to which connection may be madeto a source of heater power (not shown) through a stem lead 53, whilethe lower end of cathode portion d3 snugly receives one leg of .asubstantially U-shaped conductive connector 55, the opposite leg ofwhich is snugly fitted into the lower end opening of tubular portion 43'of cathode 19".

Conventional getter assemblies 57 can be affixed by any suitable meansto the fins.

As noted above, the subassembly is of construction generally similar tothat of the subassembly 13, just described, and corresponding parts areidentified with correspondingly primed reference numerals.

From the foregoing description, it will be appreciated that the cathodesof the respective diode subassemblies are adapted to be directly heated,heater current being applied serially through the tubular portions 45,`43 by means of the tabs 47, 49, thence through the connector 55 totubular portions 43', 45 by means of the tabs 47', 49. The heater returnis effected through stern lead 59 which is connected to the lower end ofcathode portion 45.

FIG. 2 shows a modified construction of cathode in which the upper endsof the tubular cathode portions `61, 63 are open and instead of beingprovided with interconnected tabs, as .at 47, 49 (FIG. l) are adaptedfor interconnection by means of a low-resistance U-shaped connection 65,of which the leg portions are tightly fitted into and spot-welded orotherwise secured to the open ends of the portions 61 and 63.

In FIG. 3, I have shown still another modification wherein the tubularcathode portions 67, 69` are formed of integral tubular stock having aflattened part 71 formed therein. The tubular stock can be bent adjacentthe ends of the flattened part 71 to form an inverted U-shaped parthaving a bight portion at part 71, which functions as the top connectorfor the cathodes `67, 69 without requiring .any welds or interfitting ofparts.

Advantages of the above-described directly-heated cathode rectifier willthus be apparent when it is appreciated that, by the arrangementsillustrated and described, I have provided a rectier capable of handlinglarge amounts of power with relatively small cathodeto-anode spacing,inasmuch as any bowing, vibration, or other deformation of the cathodeare virtually eliminated. At the same time, arc-over tendency has beenminimized as a result of the directly-heated character of the cathode,which, it will be observed, is now capable of substantially increasedlength over that heretofore considered possible. It will be notedfurther that my invention completely eliminates the usual folded orother conventional heater assembly, thereby eliminating another sourceof arc-Over, e.g. heater-cathode shorts, as well .as a relatively costlyassembly and troublesome assembling operation.

It will be appreciated by those skilled in the art that my invention maybe carried out in various other ways and may take various forms andembodiments other than those illustrative embodiments heretoforedescribed. It is to be understood, therefore, that the scope of theinvention is not limited by the details of the foregoing description,but will be defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electron discharge device comprising a cathode and an anode, eachcomprising a pair of hollow tubular members, `the cathode members havingportions of highresistivity material and coaxially disposed withinrespective anode members, and relatively low-resistance meansinterconnecting the cathode members for conducting electric currenttherethrough.

2. An electron discharge device comprising a cathode and an anode, eachcomprising a pair of hollow tubular members, said anode members beingdisposed in mutually spaced parallel relation, the cathode mem-bershaving portions of high-resistivity material and formed in invertedU-shape, of which the leg portions are coaxially disposed withinrespective anode members, the bight portion of said U-shapeinterconnecting the cathode members in a lowresrstance path `forconducting electric current therethrough.

3. An electron discharge device comprising a cathode and an anode, eachcomprising a pair of tubular members, the cathode `members defininglongitudinal cavities free of heat-exchanging material, said cathodemembers being coaxially disposed within respective anode members andcomprising means providing a high-resistance path on the interiorsurfaces thereof and an electron-emissive coatmg on the exteriorsurfaces thereof, and means interconnecting the cathode members in alow-resistance path for conducting electric current therethrough.

4. An electron discharge device comprising a first cathode and a firstanode, each comprising a pair of tubular members, the cores of saidcathode members being empty to minimize heat loss therein, said cathodemembers being coaxially disposed within respective anode members, meansinterconnecting the first cathode members for conducting electriccurrent therethrough, a second cathode and a second anode, eachcomprising a pair of tubular members, the -bores of said cathode membersbeing empty to minimize heat loss therein, said cathode members bingcoaxially disposed within respective anode members, meansinterconnecting the second cathode members for conducting electriccurrent therethrough, and means serially interconnecting said iirst andsaid second cathode members.

5. An electron discharge device comprising a cathode and an anode, eachcomprising a pair of hollow tubular members, the bores of said cathodemembers being void of heat-loss material, said cathode members beingcoaxially disposed within respective anode members, and tab means atadjacent ends of said cathode members, said tab means being aixed toeach other for inter-connecting thc cathode members for conductingelectric current therethrough.

6. An electron dischar-ge device comprising a cathode and an anode, eachcomprising a pair of elongated tubular members, the cathode membersdetining longitudinal cavities coextensive with the lengths of saidcathode members, said members being coaxially disposed within respectiveanode members, and U-shaped conductor means having leg portions ttedinto open-end portions of said cathode members Vfor interconnecting thecathode members.

7. An electron discharge rectifier, comprising an evacuated envelope, ananode, a cathode, and means supporting said anode and said cathode insaid envelope, said anode comprising a pair of tubular members and meansconductively connecting said members, said cathode comprising a pair oftubular members, individual ones of said cathode members being hollowand void of heat-exchanging material, said cathode members beingcoaxially disposed within individual ones of said anode members, andmeans serially interconnecting said cathode members and to a source ofcurrent.

8. A cathode assembly for an electron discharge rectifier, comprising apair of open-ended hollow tubular members, an electron-emissive coatingon the exterior surfaces of said cathode members, means defining ahigh-resistance path on the interior surfaces of said members, and meansat one pair of adjacent open ends serially interconnecting said cathodemembers.

9. The assembly -as claimed in claim 8, wherein said interconnectingmeans comprises tabs projecting in mutually opposed directions anddisposed in overlapping relation to each other, and meansinterconnecting said tags.

10. The assembly as claimed in claim 8, wherein said interconnectingmeans comprises a U-shaped conductive member having leg portions adaptedto be received in said open ends of said members.

11. The `assembly as claimed in claim 8, wherein said members areintegrally `formed o-f circular cross section stock with an intermediateportion of substantially fiattened cross section, said flattened portiondening a bend region interconnecting said members.

References Cited in the file of this patent UNITED STATES PATENTS430,933 Edison June 24, 1890 1,605,735 Hough Nov. 2, 1926 2,172,207Kolligs Sept. 5, 1939 2,181,080 Elston Nov. 21, 1939 2,244,752 WolffJune 10, 1941 2,717,975 Wihtol Sept. 13, 1955 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3,048,726 August 7, 1962Walter T. Mills s in the above numbered pat- It islhereby certified thaterror appear tters Patent should read es ent requiring correction andthat the seid Le corrected below.

Column 4, line 71, for ",lxzoregwl read bores Signed and sealed this gyof November 1962.

(SEAL) Attest: DAVID L. LADD Commissioner of Patents Attestig Officer

